Electric micro-switches are the part of electric circuits which switch them on and off. The contacts and the connections are therefore made of good electrically conductive materials. Micro-switches form a part of complex assemblies. In vehicles they are typically used in closing systems for doors, front hoods, tailgates, sliding roofs etc. They typically switch small control currents which are evaluated by microprocessors. The essential performance feature of a micro-switch is the time within which the switching operation is completed. This time is called bounce time. To ensure reliable evaluation in the control unit this bounce time must be very short and constant across the different operating states and environmental influences (e.g. temperature fluctuations).
The bounce time is influenced by the masses moved, the speed of the jump operation, the geometry of the involved contact surfaces and the electrical surface properties of the contact surfaces. In order to ensure a bounce time which is constant and low across time and environmental influences the following known values are to be aimed for:                Small moved mass. The mechanical pulse triggering the mechanical vibration increases with an increase in mass.        High jump speed (actuating speed for sliding contacts). The jump speed (for a flight of the movable contact) is constructionally given by the jump mechanism. A hard spring produces a quick jump. For sliding contacts the jump speed depends on the speed of actuation.        Constant contact geometry across all operating states and time. Deformations due to switching surges and abrasion shall not change the geometry over its lifetime. Ideally the contact surfaces touch each other in a theoretically point-like manner. In reality the contact load results in an elliptically flattened contact region, via which the current flows. This ideal contact region is to be maintained over a maximum area, even if angular deviations of the contact surfaces relative to each other occur. It is ideal if the contacts involved comprise a hardness which is high but differs between individual contacts. As a result geometry deviations and abrasions during unavoidably occurring relative movements are avoided.        Low electrical resistance in the contacting area between the contacts. The aimed for low resistance is the reason for applying precious metal layers or other contact layers in the area where the contacts touch.        Low electrical resistance is also encouraged by small point-like contact surfaces.        
All metal surfaces are coated with a continuous layer of foreign atoms. Ideally this layer of (non-conducting) foreign atoms is so thin that a tunnel current can flow through these layers (foreign platings) without resistance. This property is found in layers manufactured from hard gold. Thicker foreign coating layers may be penetrated in the contacting surfaces by strong pressing. Point-like contacting surfaces produce maximum pressing and tolerate large angular deviations without losing the point-like contact.
According to DE 10 2006 043 795 B3 contacts are formed as cylindrical hollow-form sections. With the micro-switch described here the possibility of vibrations (bouncing) occurring during the approach to a counter contact is very small (<1 ms). The mass is reduced compared to normal contacts made of solid material, so that the pulse for vibrations is reduced. The point-like contact (elliptical flattening being achieved during touching) is achieved due to the cylindrical contact surfaces arranged roughly at right angles to each other. This optimal contacting is maintained even for angle errors. Here high material hardness of the contacts involved was aimed for, the re-shaping process to obtain a cylinder supported the increase in hardness. The contact described here comprises a precious metal layer selectively applied to areas of the hollow-form section. This already led to a saving in precious metal. A selective galvanic process was used, preferably a brushing process. To reduce the precious metal to an extreme extent, application on one side only was proposed, wherein in operation the precious metal layer is achieved through material transfer from the counter contact.